[LEAPSECS] how bad precision timekeeping was

Poul-Henning Kamp phk at phk.freebsd.dk
Wed Feb 13 02:53:28 EST 2008

In message <20080213023806.GA9433 at ucolick.org>, Steve Allen writes:

>We have ample experience that nobody can tell the legislators and

>bureaucrats not to mess around with summer/daylight time transition

>dates, so we all have to deal with regular updates to the zoneinfo

>mechanisms if we want our systems to produce the legal civil time.

Correct, but for stupidity at this level, politicians can be held
accountable in their constituency.

But besides, timezones are an entirely different kettle of fish
than leap-seconds: Time-zones is just a representation format which
does not get involved until you try to represent a timestamp for a
human being, whereas leap-seconds affect the raw timestamp.

This is why ATC systems use UTC, that way an airline pilot does
not need to have a fully up to date zoneinfo file in his pocket:
part of the tower protocol is to announce the local time before
planes land, information which the captain on commercial flights
usually relays verbatim to the passengers.

>If we move the leap seconds into that same mechanism we allow the

>underlying broadcast and computer time scales to become uniformly

>monotonic. Daniel Gambis always gives more notice to the whole world

>than Hugo Chavez did to Venezuela last year.

But still not enough notice to let the computer geeks handle this
in a sane fashion.

>We have to resign ourselves to the expense of updating zoneinfo,

>or the equivalents in Windows, and cell-phone towers, and anything

>else that uses precision time and purports to supply civil time too.

If I remember the numbers right, we should expect countries to
start shifting one hour in about 150 years, right ?

150 years ago Edison was 11 years old.

But yes, zoneinfo changes must be expected, but the changes will
be national, and that means if some raving politician tries to
change the timezone with too short notice, his country have a
mechanism for dealing with him.

Nobody can seem to do much about Daniel Gambis and his short notices.

Ohh, wait...

That's what WP7A's proposal is about, isn't it ? :-)

>Yes, most actions by the ITU-R have costs to various parties.

>Despite the dissatisfaction, what the CCIR did in 1970 was a compromise.

>We have the mechanisms in place to support a compromise.

>Dropping leap seconds entirely would not be a compromise.

As I said: come up with a workable proposal, canvas it for the
right people, repeat until done.

Just crossing your arms and muttering "this isn't right" will not
stop the WP7A party.

Feel free to use me as the litmus test for your proposals, if you
think that helps save you time.


Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.

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